I know this is an old threat but seeing how I am trying to burn other things other then coal I thought I would set in a new post. Why is/was the short auger used for burning pellets? I have the 520 with the bin auger on it feeding prune pits and the burn is great but I get smoke out of the auger tube when the blower is on. I do not have an auger fire so I am not sure whats going on.

Rice coal packs tightly. You might get smoke down the short pipe with any fuel, but with rice coal, rarely down the long pipe. If your fuel doesn't pack like coal, the fan forces the smoke through the alternate fuel. You can try reducing the air setting a little.

We mixed 50/50 coal and wood pellets, maybe 30% corn/70% coal. For the price of alternatives, coal is cheap. You MUST keep an eye on these blends when burning. If they burn too deeply in the pot, discontinue use. It is possible for wood pellets to burn backwards down the coal tube when the unit is resting. Be safe. If the pipe feels very hot, stop burning the mixture.

Hummm... Okay. Not sure why I am getting the smoke then. Right now I have the bin auger on the unit. Burning 100% UAE rice coal. 5 teeth to 4.2 air. I sealed the auger coupler with RTV calk so that no air could get in that way either. I have a good draft and I am getting a nice uniform burn in the fire pot with a little bit of black coal visible in the middle when the blower is not on. I have about two feet of coal over the end of the auger and I get small wisps of smoke up through the coal bed. The auger tube is room tempt except where it goes into the stove and that is just slightly warm.

I thought you were burning prune pits? You might have negative pressure in your stoker area, maybe caused by some other exhaust fan. Dryer? Radon fan? Another stove in the house? Basement too tight? If you have good draft at the chimney, I would think that you would have no smoke in the pipe. Clean out plate fully closed?

For the last several weeks I switched back over to 100% coal due to the fact that I was getting smoke in my basement. With the pits I was getting a fair amount of smoke and thought that for the time being I would burn 100% coal until I had time to work with the issue at hand. My house was built the 1890's and other then replacement windows is original. The basement is not open but does have a garage door with some leaks around the edges. I do not have any other vents in the basement other then a forced hot air furnace that used to heat the other side of the house. All seals are tight on the fire box except the ash pan door and it is tight just not crank down on the handle tight. Every thing else has been sealed with rope gasket and then RTV calk.

It only smokes when the blower fan is running. The other furnace is hooked up to another chimney that is on the other side of the house. The furnace is off but the fan is used in conjunction with a hot water to air heat exchanger that is powered by the EFM. My basement is drafty enough that I would have to have a 500 foot smoke stack to over power the draft on my EFM chimney. Also I had Harlen Martin a long time EFM repair man look over my setup right after I fired it up. He tuned my baro with his digital meter and said everything looked good. At that time I had not noticed the smoke though. When I say faint whisps I mean you have to stand there next to the bin and stare at the coal to see the small amount of smoke coming up. I have a CO detector right over the bin and it does not go off unless of course I test it. The issue is that with the prune pits I get more smoke and it stinks. My feeling is that if I can stop the smoke with using 100% coal then I should have even less smoke with the pits. That said if I am not to have any smoke with the coal then I want to find out whats going on and of course fix it.

I don't know how tightly prune pits pack. Think of it like this: If you had air filtering up through 1/4" tiny styro pellets or 1" pellets, you would have more air passing through the larger pellets. This may be your case. How about this possibility: Your air passes through the burner plates easier on pits because they have less mass. The added volume of air pushes back in the pipe. Did you try reducing the air setting?

I don't know. It has to be related to draft. To answer your original question, I used the short pipe for two reasons. It enabled me to use a small can for my changing supply of test material and I wasn't sure the pellets would make it all the way through the long pipe without turning to powder.

Well I get them from Country Medeows in Lancaster, PA. They get them from MOTZ in Adams county. They come in raw and are processed and dried. I will pull the tube tomorrow and make sure it is installed correctly. I did check my draft today. Sucked the snicker wrapper right through the barro and up the chimney.

What are you using for oil on the coal? Perhaps it flashes off at a low temperature.

Also, are you sure the auger pipe is properly aligned in the pot? There is a hole in the air chamber casting, it is critical that the holes drilled in the auger pipe line up with that hole in the casting.